Method of producing semiconductor device

ABSTRACT

Provided is a method of manufacturing a semiconductor device which can form a high-performance photodiode in which variation in output characteristics and performance deterioration are suppressed. A prescribed gate metal is used to form a shield section  34   a  that covers a portion of a first semiconductor layer  30   a  for a photodiode that becomes an intrinsic semiconductor region on a gate insulating film  29  and to form first to fourth gate electrodes  34   b  to  34   e  that cover portions of respective second to fifth semiconductor layers  30   b  to  30   e  for thin film transistors that become channel regions on the gate insulating film  29.  Then, using the shield section  34   a  as a mask, an n-type region and p-type region are formed in the first semiconductor layer  30   a.  Then, the shield section  34   a  is removed.

TECHNICAL FIELD

The present invention relates to a method of manufacturing asemiconductor device that is used in an active matrix substrate and thelike.

BACKGROUND ART

In recent years, a liquid crystal display device, for example, has beenwidely used in a liquid crystal television, a monitor, a mobile phone,and the like as a flat panel display having characteristics, such asbeing thinner, lighter, and the like, than a conventional cathode raytube television. As such liquid crystal display devices, those using anactive matrix substrate are known. In such a liquid crystal displaydevice, a plurality of data wirings (source wirings) and a plurality ofscan wirings (gate wirings) are arranged in a matrix. In the proximityof an intersection of a data wiring and a scan wiring, a switchingelement such as a thin film transistor (TFT, hereinafter referred to as“TFT”) or the like and a pixel having a pixel electrode that isconnected to the switching element are arranged in a matrix.

In the aforementioned active matrix substrate, other than theaforementioned TFT for driving a pixel, a TFT for a peripheral circuitis integrally provided. Furthermore, when an active matrix substrate isused in a liquid crystal display device that is equipped with a touchpanel, a liquid crystal display device that is equipped with anilluminance sensor (ambient sensor), or the like, there has beensuggested that in addition to the aforementioned TFTs for driving apixel and for a peripheral circuit, a photodiode (thin film diode: TFD)be provided in the active matrix substrate. Thus, the active matrixsubstrate is a semiconductor device that is equipped with a plurality ofthin film transistors and a photodiode.

Furthermore, in the active matrix substrate, typically, TFTs havingmutually different configurations are used as TFTs for driving a pixeland for a peripheral circuit.

Specifically, as a TFT for driving a pixel, a TFT having a very low OFFleakage current is used. In a liquid crystal display device, a voltageapplied to liquid crystal needs to be sustained during one frame perioduntil the screen is updated. This is because, in a liquid crystaldisplay device, if the OFF current (OFF leakage current) of the TFT fordriving a pixel is high, the voltage applied to liquid crystal decreasesover time, causing a risk of display characteristics deterioration. As aresult, as the TFT for driving a pixel, an n-channel type TFT, forexample, having an LDD configuration in which a low-concentrationimpurity region (LDD region: Lightly Doped Drain) is formed at leasteither between a channel region and a source region of the TFT orbetween the channel region and a drain region, is typically used. Inthis LDD configuration, an LDD region having a higher resistance thanthe source region and the drain region is provided between an edge of agate electrode and the source region having a low resistance and betweenthe edge and the drain region. This way, when the aforementioned LDDconfiguration is used, the OFF leakage current can be reducedsignificantly compared to a so-called single drain configuration TFT,which does not have an LDD region.

On the other hand, as a TFT for a peripheral circuit, a TFT having ahigh current driving power, i.e., a high ON current, is used.Specifically, as the TFT for a peripheral circuit, an n-channel type TFThaving a GOLD (Gate Overlapped LDD) configuration, for example, is used.In this GOLD configuration TFT, a gate electrode overlaps an LDD region.Therefore, when a voltage is applied to the gate electrode, electronsthat become carriers are accumulated in the LDD region overlapped by thegate electrode. As a result, in the aforementioned GOLD configurationTFT, the resistance of the LDD region can be reduced. Thus, lowering ofcurrent driving power of the TFT can be suppressed, and the ON currentcan be increased.

Alternatively, in the active matrix substrate, an n-channel type TFT anda p-channel type TFT having the aforementioned single drainconfiguration are also used as TFTs for a peripheral circuit.

As a conventional method of manufacturing a semiconductor device, asdiscussed in Japanese Patent Application Laid-Open Publication No.2005-328088, for example, there has been proposed that TFTscorresponding to various circuits of an active matrix substrate beformed on a single substrate. Specifically, in this conventional methodof manufacturing a semiconductor device, an n-channel type TFT fordriving a pixel having the LDD configuration, a p-channel type TFT for aperipheral circuit having the single drain configuration, and ann-channel type TFT for a peripheral circuit having either the LDDconfiguration or the GOLD configuration are formed on a singlesubstrate.

Furthermore, as a conventional method of manufacturing a semiconductordevice, as discussed in WO 2008/133162 pamphlet, for example, there hasbeen proposed that an active matrix substrate in which a photodiode anda TFT are monolithically provided be formed. In addition, the WO2008/133162 pamphlet shows a photodiode formed of a PIN diode that isequipped with a lateral configuration. Furthermore, according to theconventional method of manufacturing a semiconductor device, variationin length of an intrinsic semiconductor region in a forward direction(i.e., channel length) can be suppressed by providing two metal wiresabove the intrinsic semiconductor region (i-layer). As a result,variation in output characteristics of the photodiode can be alsosuppressed.

SUMMARY OF THE INVENTION

However, according to the method of manufacturing a semiconductor devicediscussed in the aforementioned WO 2008/133162 pamphlet, there has beena risk of performance of the photodiode deteriorating due to the twometal wires, which are provided above the intrinsic semiconductorregion.

Specifically, in a semiconductor device that is produced by themanufacture method discussed in the aforementioned WO 2008/133162pamphlet, since light is blocked by the metal wires, there has been arisk of the light receiving area of an intrinsic semiconductor regionthat constitutes a light detection area becoming smaller, therebycausing a photocurrent to be reduced. Moreover, in the semiconductordevice produced by the aforementioned manufacture method, there has beena risk of an interference of light that was reflected by metal wires andlight entering the photodiode (intrinsic semiconductor region)occurring, thereby decreasing the amount of light entering the intrinsicsemiconductor region. As described, in the semiconductor device producedby the aforementioned manufacture method, there has been a risk ofdetection accuracy of the photodiode lowering.

Furthermore, in the method of manufacturing a semiconductor devicediscussed in the aforementioned WO 2008/133162 pamphlet, the respectivemetal wires are formed using dry etching so that edges of the respectivemetal wires are located above the intrinsic semiconductor region.Because of this, there has been a risk that an etching damage caused bythe dry etching is left in the intrinsic semiconductor region. Thus,there has been a risk of an S/N ratio lowering in output of thephotodiode.

In order to address the aforementioned problems, an object of thepresent invention is to provide a method of manufacturing asemiconductor device that can form a high performance photodiode thatsuppresses variation in output characteristics and performancedeterioration.

In order to achieve the aforementioned object, a method of manufacturinga semiconductor device according to an embodiment of the presentinvention is a method of manufacturing a semiconductor device having aphotodiode and a thin film transistor on the same substrate, includingthe following steps: (a) forming a first semiconductor layer for thephotodiode and a second semiconductor layer for the thin film transistoron the substrate; (b) forming a gate insulating film that covers thefirst and second semiconductor layers; (c) forming a first gateelectrode that covers a portion of the second semiconductor layer thatbecomes a channel region on the gate insulating film using a prescribedgate metal, and forming a shield section that covers a portion of thefirst semiconductor layer that becomes an intrinsic semiconductor regionon the gate insulating film using the gate metal; (d) implanting a firstconductive type impurity into the first and second semiconductor layersfrom above the gate insulating film to form a region where the firstconductive type impurity is implanted in a region of the firstsemiconductor layer that is not covered by the shield section and toform a region where the first conductive type impurity is implanted in aregion of the second semiconductor layer that is not covered by thefirst gate electrode; (e) forming a first resist having an opening thatexposes a portion of the gate insulating film, which covers the firstsemiconductor layer, and implanting a second conductive type impurityfrom above the gate insulating film to form a second conductive typeregion in a region of the first semiconductor layer that is not coveredby the shield section or the first resist; (f) forming a second resistthat covers the second conductive type region of the first semiconductorlayer and implanting the first conductive type impurity from above thegate insulating film to form a first conductive type region in a regionof the first semiconductor layer that is not covered by the shieldsection or the second resist; and (g) removing the shield section.

According to the present invention, a method of manufacturing asemiconductor device that can form a high performance photodiode thatsuppresses variation in output characteristics and performancedeterioration can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a drawing explaining a configuration of a liquid crystaldisplay device according to an embodiment of the present invention.

FIG. 2 is a drawing explaining a configuration of basic parts of theaforementioned liquid crystal display device.

FIG. 3 is a drawing schematically showing a configuration of pixels ofthe aforementioned liquid crystal display device.

FIG. 4 is an equivalent circuit diagram showing a configuration ofpixels and an optical sensor provided in the aforementioned liquidcrystal display device.

FIG. 5 is a drawing explaining process steps of a photodiode and thinfilm transistors provided in the aforementioned liquid crystal displaydevice. FIG. 5( a) to FIG. 5( c) explain a set of main process steps.

FIG. 6 is a drawing explaining process steps of the photodiode and thethin film transistors provided in the aforementioned liquid crystaldisplay device. FIG. 6( a) to FIG. 6( c) explain a set of main processsteps performed after the step shown in FIG. 5( c).

FIG. 7 is a drawing explaining process steps of the photodiode and thethin film transistors provided in the aforementioned liquid crystaldisplay device. FIG. 7( a) to FIG. 7( c) explain a set of main processsteps performed after the step shown in FIG. 6( c).

FIG. 8 is a drawing explaining process steps of the photodiode and thethin film transistors provided in the aforementioned liquid crystaldisplay device. FIG. 8( a) to FIG. 8( c) explain a set of main processsteps performed after the step shown in FIG. 7( c).

FIG. 9 is a drawing comparing variation in the dimension of an intrinsicsemiconductor region between when a conventional method is used and whena method according to the present embodiment is used.

DETAILED DESCRIPTION OF EMBODIMENTS

A method of manufacturing a semiconductor device according to anembodiment of the present invention is a method of manufacturing asemiconductor device having a photodiode and a thin film transistor onthe same substrate, which includes the following steps: (a) forming afirst semiconductor layer for the photodiode and a second semiconductorlayer for the thin film transistor on the substrate; (b) forming a gateinsulating film that covers the first and second semiconductor layers;(c) forming a first gate electrode that covers a portion of the secondsemiconductor layer that becomes a channel region on the gate insulatingfilm using a prescribed gate metal, and forming a shield section thatcovers a portion of the first semiconductor layer that becomes anintrinsic semiconductor region on the gate insulating film using thegate metal; (d) implanting a first conductive type impurity into thefirst and second semiconductor layers from above the gate insulatingfilm to form a region where the first conductive type impurity isimplanted in a region of the first semiconductor layer that is notcovered by the shield section and to form a region where the firstconductive type impurity is implanted in a region of the secondsemiconductor layer that is not covered by the first gate electrode; (e)forming a first resist having an opening that exposes a portion of thegate insulating film, which covers the first semiconductor layer, andimplanting a second conductive type impurity from above the gateinsulating film to form a second conductive type region in a region ofthe first semiconductor layer that is not covered by the shield sectionor the first resist; (f) forming a second resist that covers the secondconductive type region of the first semiconductor layer and implantingthe first conductive type impurity from above the gate insulating filmto form a first conductive type region in a region of the firstsemiconductor layer that is not covered by the shield section or thesecond resist; and (g) removing the shield section.

In each of the respective steps of forming the first and secondconductive type regions of the photodiode, if a resist is formed on aregion that becomes an intrinsic semiconductor region, dimensionalaccuracy of the intrinsic semiconductor region is affected bydimensional accuracy and alignment of the respective resists. Incontrast, in the aforementioned method of manufacturing a semiconductordevice, a shield section is formed to cover a portion of the photodiodethat becomes the intrinsic semiconductor region using a gate metal. As aresult, in the aforementioned method of manufacturing a semiconductordevice, only dimensional variation of the shield section and errorsduring etching affect variation in the dimension of the intrinsicsemiconductor region. Therefore, variation in the length of theintrinsic semiconductor region in the forward direction, i.e., thechannel length variation of the photodiode, is reduced. As a result,variation in output characteristics of the photodiode can be suppressed.

Furthermore, according to the aforementioned method of manufacturing asemiconductor device, the first and second conductive type regions areformed in the first semiconductor layer using the shield section as aresist (mask), and then, the shield section is removed. This way,decrease in the light receiving area of the intrinsic semiconductorregion and decrease in the amount of light entering the intrinsicsemiconductor region, which occur in the aforementioned conventionalexample, can be prevented. Therefore, according to the aforementionedmethod, decrease in photocurrent flowing into the photodiode can beprevented. Furthermore, even when the shield section is formed using dryetching, etching damages at edges of the shield section are on the firstand second conductive type regions. Therefore, lowering of the S/N ratiodoes not occur in output of the photodiode.

As a result, a high performance photodiode that suppresses variation inoutput characteristics of the photodiode and that suppresses performancedeterioration of the photodiode can be formed.

In the aforementioned method of manufacturing a semiconductor device, inthe step (e), a third resist that entirely covers the secondsemiconductor layer may be formed to prevent the second conductive typeimpurity from being implanted into the second semiconductor layer, andin the step (f), a fourth resist having an opening that exposes portionsof the gate insulating film that are located on both sides of the secondsemiconductor layer with the gate electrode located therebetween in aplan view may be formed so that one and the other of a source region anda drain region may be respectively formed in regions of both sides ofthe second semiconductor layer that are not covered by the first gateelectrode or the fourth resist, and a region of the second semiconductorlayer that is covered by the fourth resist may become alow-concentration impurity region to form a first conductive type thinfilm transistor having an LDD configuration as the first of the thinfilm transistor. In this case, the first conductive type thin filmtransistor having an LDD configuration can be formed at the same time asthe photodiode.

In the aforementioned method of manufacturing a semiconductor device, inthe step (a), a third semiconductor layer for a second thin filmtransistor may be formed on the substrate. In the step (b), a gateinsulating film that covers the first to third semiconductor layers maybe formed. Before performing the step (c), the method may furtherinclude a step (h) of forming fifth and sixth resists that respectivelycover the first and second semiconductor layers entirely and forming aseventh resist that covers a portion of the third semiconductor layerthat becomes a channel region, and implanting a first conductive typeimpurity into the third semiconductor layer from above the gateinsulating film to form a region in which the first conductive typeimpurity is implanted in a region of the third semiconductor layer thatis not covered by the seventh resist. In the step (c), a second gateelectrode that covers portions of the third semiconductor layer thatbecome a channel region and a low-concentration impurity region may beformed on the gate insulating film using the gate metal. In the step(d), the channel region and the low-concentration impurity region may beformed in a region that is covered by the second gate electrode. In thestep (e), an eighth resist that entirely covers the third semiconductorlayer may be formed to prevent the second conductive type impurity frombeing implanted to the third semiconductor layer, and in the step (f),one and the other of a source region and a drain region may berespectively formed in regions of the third semiconductor layer that arenot covered by the second gate electrode to form a first conductive typethin film transistor having a GOLD configuration as the second thin filmtransistor. In this case, the first conductive type thin film transistorhaving the GOLD configuration can be formed at the same time as thephotodiode.

In the aforementioned method of manufacturing a semiconductor device, inthe step (a), a fourth semiconductor layer for a third thin filmtransistor may be formed on the substrate. In the step (b), a gateinsulating film that covers the first to fourth semiconductor layers maybe formed. In the step (h), a ninth resist that entirely covers thefourth semiconductor layer may be formed. In the step (c), a third gateelectrode that covers a portion of the fourth semiconductor layer thatbecomes a channel region may be formed on the gate insulating film usingthe gate metal. In the step (d), a region in which the first conductivetype impurity is implanted may be formed in a region of the fourthsemiconductor layer that is not covered by the third gate electrode. Inthe step (e), a tenth resist that entirely covers the fourthsemiconductor layer may be formed to prevent the second conductive typeimpurity from being implanted to the fourth semiconductor layer, and inthe step (f), one and the other of a source region and a drain regionmay be respectively formed in regions of the fourth semiconductor layerthat are not covered by the third gate electrode to form a firstconductive type thin film transistor having a Single Drain configurationas the third thin film transistor. In this case, the first conductivetype thin film transistor having a Single Drain configuration can beformed at the same time as the photodiode.

In the aforementioned method of manufacturing a semiconductor device, inthe step (a), a fifth semiconductor layer for a fourth thin filmtransistor may be formed on said substrate. In the step (b), a gateinsulating film that covers the first to fifth semiconductor layers maybe formed. In the step (h), an eleventh resist that entirely covers thefifth semiconductor layer may be formed. In the step (c), a fourth gateelectrode that covers a portion of the fifth semiconductor layer thatbecomes a channel region may be formed on the gate insulating film usingthe gate metal. In the step (d), a region in which the first conductivetype impurity is implanted may be formed in a region of the fifthsemiconductor layer that is not covered by the fourth gate electrode. Inthe step (e), one and the other of a source region and a drain regionmay be respectively formed in regions of the fifth semiconductor layerthat are not covered by the fourth gate electrode to form a secondconductive type thin film transistor as the fourth thin film transistor.In the step (f), a twelfth resist that entirely covers the fifthsemiconductor layer may be formed to prevent the first conductive typeimpurity from being implanted to the fifth semiconductor layer. In thiscase, a second conductive type thin film transistor can be formed at thesame time as the photodiode.

In the aforementioned method of manufacturing a semiconductor device, inthe step (c), after the gate metal is formed on the gate insulating filmso as to entirely cover the first to fifth semiconductor layers,thirteenth, fourteenth, fifteenth, sixteenth, and seventeenth resistsmay be formed at portions that become the shield section, the first, thesecond, the third, and the fourth gate electrodes, respectively. Then, aprescribed etching treatment may be performed to form the shield sectionand the first to fourth gate electrodes on the gate insulating film. Inthis case, the shield section and the first to fourth gate electrodescan be formed at appropriate locations with ease.

In the aforementioned method of manufacturing a semiconductor device,after the step (b), the method may further include a step (i) ofimplanting the first or the second conductive type impurity into thefirst to the fifth semiconductor layers from above the gate insulatingfilm to adjust the resistance of the respective first to fourth thinfilm transistors. In this case, the resistance of the respective firstto fourth thin film transistors can be set at appropriate values withease.

In the aforementioned method of manufacturing a semiconductor device,after the step (g), the method may further include a step (j) ofimplanting the first or the second conductive type impurity into thefirst semiconductor layer from above the gate insulating film to adjustthe resistance of the photodiode. In this case, the resistance of thephotodiode can be set to an appropriate value with ease.

In the aforementioned method of manufacturing a semiconductor device,the first conductive type may be an n-type, and the second conductivetype may be a p-type. In this case, a lateral configuration photodiodeand an n-type and/or a p-type thin film transistor can be integrallyformed.

Embodiment

A method of manufacturing a semiconductor device according to anembodiment of the present invention is described below with reference tofigures. In the description below, a case in which the present inventionis applied to an active matrix substrate that is used in a liquidcrystal display device having a touch panel is shown as an example.Dimensions of components in the respective figures do not show the exactdimensions of the actual components, dimensional ratio of the respectivecomponents, and the like.

FIG. 1 is a drawing explaining a configuration of a liquid crystaldisplay device according to an embodiment of the present invention. InFIG. 1, a liquid crystal display device 1 according to the presentembodiment has a liquid crystal panel 2, which is a display section thatis disposed with the upper side of FIG. 1 as the viewing side (displaysurface side), and an illumination device 3, which is an illuminationsection that is disposed on the non-display surface side (lower side ofFIG. 1) of the liquid crystal panel 2 and that irradiates the liquidcrystal panel 2 with illumination light. Furthermore, a touch panel thatis equipped with an optical sensor, which is described later, isintegrally built into the liquid crystal display device 1. The liquidcrystal display device 1 is configured such that prescribed touch panelfunctions, such as detecting operation of operational input command by auser and the like, can be performed by the touch panel.

The liquid crystal panel 2 has a color filter substrate 4 and an activematrix substrate 5, which constitute a pair of substrates, andpolarizing plates 6 and 7 that are disposed so as to cover the colorfilter substrate 4 and the active matrix substrate 5, which overlap witheach other, from both sides. Between the color filter substrate 4 andthe active matrix substrate 5, a liquid crystal layer, which isdescribed later, is interposed. The polarizing plate 6, 7 is attached tothe corresponding color filter substrate 4 or active matrix substrate 5to cover at least an effective display region of the display surfaceprovided in the liquid crystal panel 2.

Between the active matrix substrate 5 and the liquid crystal layer,pixel electrodes, thin film transistors (hereinafter abbreviated as“TFTs”), and the like, which correspond to a plurality of pixelsincluded in the display surface of the liquid crystal panel 2, areformed (described in detail later). The active matrix substrate 5, asdescribed later, is a semiconductor device in which photodiodes (thinfilm diodes: TFDs) and TFTs of a plurality of types are monolithicallyformed. Between the color filter substrate 4 and the liquid crystallayer, a color filter, which is described later, an opposite electrode,and the like are formed.

Furthermore, the liquid crystal panel 2 is equipped with an FPC(Flexible Printed Circuit) 8 that is connected to a control device (notshown in the figure) that controls drive of the liquid crystal panel 2.As described, the liquid crystal display device 1 can display a desiredimage on the display surface of the liquid crystal panel 2 by operatingthe liquid crystal layer on a pixel by pixel basis.

The illumination device 3 has a cold cathode fluorescent lamp 9 as thelight source and a light guide plate 10 that is disposed to face thecold cathode fluorescent lamp 9. Furthermore, in the illumination device3, in a state in which the liquid crystal panel 2 is disposed on theviewing side of the light guide plate 10, the cold cathode fluorescentlamp 9 and the light guide plate 10 are supported by a bezel 14. On thecolor filter substrate 4, a case 11 is arranged. This way, theillumination device 3 is built into the liquid crystal panel 2 to beunified with the liquid crystal panel 2. Thus, the illumination device 3and the liquid crystal panel 2 constitute the transmissive liquidcrystal display device 1 in which illumination light from theillumination device 3 enters the liquid crystal panel 2.

Light from the cold cathode fluorescent lamp 9 enters the light guideplate 10, which is formed of a synthetic resin, such as a transparentpolycarbonate resin or the like, for example. On the light guide plate10, a reflection sheet 12 is disposed on the surface opposite from theliquid crystal panel 2. In addition, on the surface of the light guideplate 10 on the liquid crystal panel 2 side, optical sheets 13, such asa lens sheet, a diffusion sheet, and the like, are provided. The coldcathode fluorescent lamp 9, the light guide plate 10, the reflectionsheet 12, and the optical sheets 13 function as a planar light sourcethat irradiates the liquid crystal panel 2 with light.

Next, with reference to FIGS. 2 to 4, each component of the liquidcrystal display device 1 of the present embodiment is described indetail.

FIG. 2 is a drawing explaining a configuration of primary parts of theliquid crystal display device 1. FIG. 3 is a magnified cross-sectionalview showing a specific configuration of a pixel of the liquid crystaldisplay device 1. FIG. 4 is an equivalent circuit diagram showing aconfiguration of a pixel and an optical sensor provided in the liquidcrystal display device 1.

As shown in FIG. 2, in the liquid crystal display device 1 of thepresent embodiment, a pixel region 17, a display gate driver 18, adisplay source driver 19, a sensor column driver 20, a sensor row driver21, and a buffer amplifier 22 are provided on the active matrixsubstrate 5. The display gate driver 18 and the display source driver 19are connected to an LCD drive section 15 through an FPC (FlexiblePrinted Circuit), which is not shown in the figure. The sensor columndriver 20, the sensor row driver 21, and the buffer amplifier 22 areconnected to a touch panel drive section 16 through another FPC (notshown in the figure).

The aforementioned respective components on the active matrix substrate5 may be monolithically formed on a transparent substrate such as atransparent glass substrate or the like. Alternatively, among theaforementioned respective components, a driver or the like may bemounted on the transparent substrate by a COG (Chip On Glass) techniqueor the like, for example.

The configuration may not be limited to the aforementionedconfiguration. A single FPC may be used to connect the display gatedriver 18 and the display source driver 19 to the LCD drive section 15and to connect the sensor column driver 20, the sensor row driver 21,and the buffer amplifier 22 to the touch panel drive section 16.

The pixel region 17 constitutes the display surface of the liquidcrystal panel 2, and is provided with a plurality of pixels arranged ina matrix. In addition, the pixel region 17 is provided with an opticalsensor for each pixel unit.

Specifically, as shown in FIG. 3, in the liquid crystal panel 2, colorfilters 24 r, 24 g, and 24 b of red (R), green (G), and blue (B),respectively, are formed on the surface of the color filter substrate 4on the liquid crystal layer 23 side. In the liquid crystal panel 2,pixels Pr, Pg, and Pb of the respective colors RGB are providedcorresponding to the color filters of the respective colors 24 r, 24 g,and 24 b.

On the other hand, on the active matrix substrate 5, a switchingelement, which is described later, is formed for each pixel.Furthermore, the active matrix substrate 5 is provided with alight-receiving element (photodiode D1) of an optical sensor 25 inaddition to the aforementioned switching element in the pixel region. Asshown in FIG. 3, the light-receiving element of the optical sensor 25 isprovided in the pixel Pr, for example, among pixels Pr, Pg, and Pb, andreceives light entering from outside the display surface. FIG. 3schematically shows a configuration of a pixel, and is different fromthe configuration of the actual cross-section.

In the aforementioned touch panel, the light-receiving element of theoptical sensor 25 receives reflected light from a reflection object(detection object) such as a finger or the like to perform a coordinatedetecting operation in which the optical sensor 25 detects coordinates(location) indicated by a touch operation of a user or the like. In thetouch panel, a prescribed touch panel operation, such as a detectingoperation of an operational input command by a user or the like isperformed using the results of the coordinate detecting operation.

As shown in FIG. 4, in the pixel region 17, a gate line Gn and sourcelines Srm, Sgm, and Sbm arranged in a matrix are provided as wirings forpixels. The gate line Gn is connected to the display gate driver 18. Thesource lines Srm, Sgm, and Sbm correspond to the respective colors ofRGB, and are respectively connected to the display source driver 19.

At intersections of the gate line Gn and the source lines Srm, Sgm, andSbm, thin film transistors (TFTs) M1 r, M1 g, and M1 b for drivingpixels are provided respectively. In the pixel Pr, the gate electrode ofthe thin film transistor M1 r is connected to the gate line Gn; thesource electrode is connected to the source line Srm; and the drainelectrode is connected to the pixel electrode, which is not shown in thefigure, respectively. This way, as shown in FIG. 4, in the pixel Pr, aliquid crystal capacitance LC is formed between the drain electrode ofthe thin film transistor M1 r and an opposite electrode (VCOM).Furthermore, an auxiliary capacitance LS is formed parallel to theliquid crystal capacitance LC. Here, the aforementioned respective thinfilm transistors M1 r, M1 g, and M1 b, as described in detail later, areconstituted of n-type (n-channel) TFTs having an LDD configuration, forexample.

Similarly, also in the pixel Pg, the gate electrode of the thin filmtransistor M1 g is connected to the gate line Gn; the source electrodeis connected to the source line Sgm; and the drain electrode isconnected to the pixel electrode, which is not shown in the figure,respectively. This way, as shown in FIG. 4, in the pixel Pg, a liquidcrystal capacitance LC is also formed between the drain electrode of thethin film transistor M1 g and an opposite electrode (VCOM). Furthermore,an auxiliary capacitance LS is formed parallel to the liquid crystalcapacitance LC.

Also, in the pixel Pb, the gate electrode of the thin film transistor M1b is connected to the gate line Gn; the source electrode is connected tothe source line Sbm; and the drain electrode is connected to the pixelelectrode, which is not shown in the figure, respectively. This way, asshown in FIG. 4, in the pixel Pb, a liquid crystal capacitance LC isalso formed between the drain electrode of the thin film transistor M1 band an opposite electrode (VCOM). Furthermore, an auxiliary capacitanceLS is formed parallel to the liquid crystal capacitance LC.

To the respective pixels Pr, Pg, and Pb, voltage signals (gradationvoltages) according to the luminance (gradation) of the respectivepixels when information is displayed on the aforementioned displaysurface are supplied from the display source driver 19 through thesource lines Srm, Sgm, and Sbm, which correspond to the respectivepixels Pr, Pg, and Pb.

Thus, as shown in FIG. 2, the LCD drive section 15 is provided with apanel control section 15 a and an illumination control section 15 b. Tothe panel control section 15 a, image signals of information to bedisplayed on the display surface are inputted from outside the liquidcrystal display device 1. The panel control section 15 a generates therespective command signals to output to the display gate driver 18 andthe display source driver 19 according to the inputted image signals.

This way, the display gate driver 18 sequentially outputs gate signalsfor turning on the gate electrode of the corresponding thin filmtransistors M1 r, M1 g, and M1 b to a plurality of gate lines Gn basedon the command signal from the panel control section 15 a. On the otherhand, the display source driver 19 supplies the aforementioned gradationvoltages to the respective pixels Pr, Pg, and Pb through thecorresponding source lines Srm, Sgm, and Sbm, based on the commandsignal from the panel control section 15 a.

To the illumination control section 15 b, an illumination adjustmentcommand signal that instructs a change in luminance of theaforementioned illumination light is inputted from a controller or thelike provided in the liquid crystal display device 1. The illuminationcontrol section 15 b is configured such that it controls power suppliedto the cold cathode fluorescent lamp 9 of the illumination device 3based on the inputted illumination adjustment command signal.

Going back to FIG. 4, the optical sensor 25 has the photodiode D1, whichis the aforementioned light-receiving element, a capacitor C1, and thinfilm transistors M2 to M4. Furthermore, in the optical sensor 25, aconstant voltage is supplied from the sensor column driver 20 throughwires VSSj and VSDj that are provided parallel to the source lines Srmand Sbm, respectively. Furthermore, the optical sensor 25 is configuredsuch that it outputs detection results to a sensor column pixel readoutcircuit 20 a of the sensor column driver 20 through a wire OUTj arrangedparallel to the source line Sgm. The photodiode D1, as described indetail later, is constituted of a PIN photodiode of a lateral structure.

A wire RSTi for supplying reset signals is connected to the thin filmtransistor M4. A wire RWSi for supplying readout signals is connected tothe thin film transistor M3. These wires RSTi and RWSi are connected thesensor row driver 21.

As shown in FIG. 2, the sensor column driver 20 has the sensor columnpixel readout circuit 20 a, a sensor column amplifier 20 b, and a sensorcolumn scanning circuit 20 c. The sensor column driver 20 operatesaccording to command signals from the optical sensor control section 16a of the touch panel drive section 16. Detection results (voltagesignals) of the plurality of optical sensors 25 arranged in a matrix inthe pixel region 17 are successively inputted to the sensor column pixelreadout circuit 20 a through the wire OUTj. The sensor column pixelreadout circuit 20 a outputs the inputted voltage signals to the sensorcolumn amplifier 20 b.

The sensor column amplifier 20 b has a plurality of built-in amplifiers(not shown in the figure) provided corresponding to the plurality ofoptical sensors 25, and amplifies the corresponding voltage signals tooutput to the buffer amplifier 22. The sensor column scanning circuit 20c outputs column selecting signals for successively connecting theplurality of amplifiers of the sensor column amplifier 20 b to thebuffer amplifier 22 to the sensor column amplifier 20 b according tocommand signals from the optical sensor control section 16 a. This way,voltage signals after amplification are outputted from the sensor columnamplifier 20 b to the touch panel drive section 16 side through thebuffer amplifier 22.

The sensor row driver 21 is provided with a sensor row level shifter 21a that uses a shift register and a sensor row scanning circuit 21 b. Thesensor row scanning circuit 21 b successively selects the wires RSTi andRWSi with a prescribed time interval according to command signals fromthe optical sensor control section 16 a. This way, in the pixel region12, the optical sensor 25 from which the readout voltage signal is to beread out (detection results) is successively selected row by row.

Here, a case in which a single optical sensor 25 is provided for a setof RGB pixels Pr, Pg, and Pb in the pixel region 17 was described.However, the number of the optical sensor 25 disposed in the pixelregion 17, locations where components such as the photodiode D1 and thelike included in the optical sensor 25 are arranged, and the like arenot limited to the aforementioned configuration, and can be selectedflexibly. For example, a photodiode (light receiving element) D1 thatperforms actual light detection may be provided in each of the pixelsPr, Pg, and Pb to have a configuration in which the optical sensor 25 isprovided for each pixel.

As shown in FIG. 2, the touch panel drive section 16 has the opticalsensor control section 16 a and a signal processing section 16 b. Thetouch panel drive section 16 controls drive of each of the plurality ofoptical sensors 25, and based on the respective detection results of theplurality of optical sensors 25, performs a prescribed touch paneloperation, such as detection of an operational input command by a touchoperation of a user or the like.

When the power of the liquid crystal display device 1 is turned on, forexample, the optical sensor control section 16 a outputs a drive commandsignal to the sensor column driver 20 and the sensor row driver 21 sothat the optical sensor 25 performs a sensing operation. Thus, when theliquid crystal display device 1 is in operation, the optical sensorcontrol section 16 a makes the optical sensors 25 perform a coordinatedetecting operation to detect a touch operation by a user. Detectionresults of the optical sensors 25 are stored in a memory (not shown inthe figure) provided in the touch panel drive section 16.

The signal processing section 16 b is configured such that it executes aprescribed touch panel operation including detecting operation of anoperational input command by a user. Specifically, the signal processingsection 16 b obtains location (coordinates) information of a finger of auser or the like on the display surface of the aforementioned liquidcrystal panel using detection results (i.e., coordinate detectingoperation results) of the optical sensor 25 stored in the aforementionedmemory. When a user's finger is placed on a desired location of anoperation input screen (command input screen, for example) displayed onthe liquid crystal panel 2, light emitted from the liquid crystal panel2 side is reflected by the finger to the liquid crystal panel 2 side.The optical sensors 25 that are located near a location directly belowthe desired location detect the reflected light. Then, based on thelocation of the optical sensors 25, which detected the reflected light,the signal processing section 16 b obtains positional information of thetouch operation location of the user on the command input screen.Detecting operation of an operational input command by a user isperformed this way in the liquid crystal display device 1 of the presentembodiment.

The configuration is not limited to the aforementioned configuration. Aconfiguration in which a scanning operation that scans image informationis performed by a touch panel may be adopted.

Here, the touch panel drive section 16, the sensor column driver 20, thesensor row driver 21, the buffer amplifier 25, and the optical sensor 25are built into the liquid crystal display device 1 of the presentembodiment to constitute a touch panel that performs a prescribed touchpanel function.

With reference to FIGS. 5 to 8, a method of manufacturing the activematrix substrate 5 according to the present embodiment is described indetail. Below, a manufacture method in which a photodiode that isconstituted of the aforementioned PIN diode, an n-channel type (n-type)TFT of LDD configuration, an n-channel type (n-type) TFT of GOLDconfiguration, and n-channel type (n-type) and p-channel type (p-type)TFTs of single drain configuration are provided on a single substrate isdescribed as an example. The aforementioned thin film transistor fordriving pixels is an n-channel type (n-type) TFT of LDD configuration. Athin film transistor for a peripheral circuit is an n-channel type(n-type) TFT of GOLD configuration, an n-channel type (n-type) TFT ofSingle Drain configuration, or a p-channel type (p-type) TFT of SingleDrain configuration.

FIG. 5 is a drawing explaining steps of manufacturing a photodiode andthin film transistors provided in the aforementioned liquid crystaldisplay device. FIG. 5( a) to FIG. 5( c) explain a set of main processsteps. FIG. 6 is a drawing explaining process steps of the photodiodeand the thin film transistor provided in the aforementioned liquidcrystal display device. FIG. 6( a) to FIG. 6( c) explain a set of mainprocess steps performed after the step shown in FIG. 5( c). FIG. 7 is adrawing explaining process steps of the photodiode and the thin filmtransistors provided in the aforementioned liquid crystal displaydevice. FIG. 7( a) to FIG. 7( c) explain a set of main process stepsperformed after the step shown in FIG. 6( c). FIG. 8 is a drawingexplaining process steps of the photodiode and the thin film transistorsprovided in the aforementioned liquid crystal display device. FIG. 8( a)to FIG. 8( c) explain a set of main process steps performed after thestep shown in FIG. 7( c).

A base substrate 5′ constitutes a base material of the active matrixsubstrate 5. For the base substrate 5′, other than a quartz substrateand a glass substrate, a substrate having an insulating surface, such asa Si substrate, a metal substrate, or the like, that has a surfacecoated with an insulating layer, is used.

As shown in FIG. 5( a), a light-shielding film 26 is formed on a portionof the surface of the base substrate 5′ where the photodiode is to beformed. Then, an insulating film 27 is formed on the overall surface ofthe base substrate 5′ including the light-shielding film 26.

For the light-shielding film 26, a metal film formed of a metal that hasa high melting point, such as tantalum (Ta), tungsten (W), molybdenum(Mo), or the like, for example, is used. The light-shielding film 26 isformed to be 30 nm to 200 nm in thickness, for example. Thelight-shielding film 26 prevents light from entering the photodiode fromthe back surface direction of the substrate (lower direction in thefigure). The insulating film 27 is formed of a silicon oxide film, asilicon nitride film, or a silicon oxynitride film, for example. Theinsulating film 27 is formed by a plasma CVD method, for example, tohave a prescribed thickness (500 nm, for example). Other than theaforementioned description, when a substrate that is not transparent isused as the base substrate 5′, the light-shielding film 26 may beomitted.

Next, as shown in FIG. 5( b), island-shaped first, second, third,fourth, and fifth semiconductor layers 28 a, 28 b, 28 c, 28 d, and 28 eare formed on the insulating film 27. Then, a gate insulating film 29that covers these semiconductor layers 28 a to 28 e is formed.

The first semiconductor layer 28 a constitutes an active layer of theaforementioned photodiode. The second to fifth semiconductor layers 28 bto 28 e constitute the respective active layers of the aforementionedn-channel type TFT of LDD configuration, n-channel type TFT of GOLDconfiguration, n-channel type TFT of Single Drain configuration, andp-channel type TFT of Single Drain configuration, which are the first tofourth thin film transistors.

The first to fifth semiconductor layers 28 a to 28 e are formed using acrystalline silicon film. Specifically, first, using a known method suchas a plasma CVD method, a sputtering method, or the like, asemiconductor film having an amorphous structure (here, an amorphoussilicon film) is deposited. The thickness of the amorphous silicon filmis set to 20 nm or more and 100 nm or less, for example. If theinsulating film 27 and the amorphous silicon film are formed by the samemethod, they may be formed continuously. Then, the amorphous siliconfilm is crystallized to obtain a crystalline silicon film.Crystallization of the amorphous silicon film can be performed using aknown method. The amorphous silicon film may be crystallized byirradiating the amorphous silicon film with laser light, for example. Aslaser light, excimer laser light of pulse oscillation type or continuousoscillation type is preferable. However, an argon laser light ofcontinuous oscillation type may be used. Furthermore, a catalyst element(Ni or the like, for example) for facilitating crystallization may beattached to a surface of the amorphous silicon, and the amorphoussilicon film may be crystallized by a thermal treatment (laserirradiation, for example). The obtained crystalline silicon film ispatterned by photolithography and etching to obtain the first to fifthsemiconductor layers 28 a to 28 e.

A silicon oxide (SiO₂) film of 100 nm thick, for example, is formed asthe gate insulating film 29. Formation of the gate insulating film 29may be performed using a CVD method, for example. Other than theaforementioned description, the gate insulating film 29 may be formedusing a silicon nitride film, for example.

Next, in FIG. 5( c), a first or second conductive type (n-type orp-type) impurity is implanted to the first to fifth semiconductor layers28 a to 28 e from above the gate insulating film 29 to adjust theresistance of the respective first to fourth thin film transistors.Specifically, on the overall surface of the gate insulating film 29,p-type low-concentration impurity ions (boron ions, for example), forexample, are implanted to the first to fifth semiconductor layers 28 ato 28 e to adjust the resistance of the respective first to fourth thinfilm transistors. This way, the first to fifth semiconductor layers 28 ato 28 e become first to fifth semiconductor layers 30 a to 30 e,respectively. According to the aforementioned step, the resistance ofthe respective first to fourth thin film transistors can be set atappropriate values with ease. The accelerating voltage during boron ionimplantation is set at 80 kV, and the dose amount is set at 1×10¹³/cm²,for example.

Next, as shown in FIG. 6( a), resists r1, r2, r3, r4, and r5 are formedas masks on the gate insulating film 29. Specifically, the resist r1,which is a fifth resist, is formed so as to cover the overall firstsemiconductor layer 30 a, and the resist r2, which is a sixth resist, isformed so as to cover the overall second semiconductor layer 30 b. Theresist r3, which is a seventh resist, is formed so as to cover a portionof the third semiconductor layer 30 c that becomes a channel region. Inaddition, the resist r4, which is a ninth resist, is formed so as tocover the overall fourth semiconductor layer 30 d, and the resist r5,which is an eleventh resist, is formed so as to cover the overall fifthsemiconductor layer 30 e.

Then, n-type low-concentration impurity ions (phosphorus ions, forexample) are implanted from above the resists r1 to r5 to form impurityimplanted regions 32 and 33 in the third semiconductor layer 30 c. Theimpurity implanted regions 32 and 33, as described later, become LDDregions, a source region, or a drain region of the GOLD configurationTFT. On the other hand, a region 31 of the third semiconductor layer 30c where phosphorus ions were not implanted becomes a channel region ofthe GOLD configuration TFT. In the first, second, fourth, and fifthsemiconductor layers 30 a, 30 b, 30 d, and 30 e, implantation ofphosphorus ions is prevented by the corresponding resists r1, r2, r4,and r5. The accelerating voltage during phosphorus ion implantation isset at 80 kV, and the dose amount is set at 1×10¹³/cm², for example.

Next, as shown in FIG. 6( b), a gate metal 34 is formed on the gateinsulating film 29 so as to cover the overall first to fifthsemiconductor layers 30 a to 30 e. A tungsten film of 400 nm inthickness, for example, is used as the gate metal 34. This tungsten filmis deposited on the gate insulating film 29 by a sputtering method.Then, resists r6, r7, r8, r9, and r10, which are masks, are formed onthe gate metal 34. Specifically, the resist r6, which is a thirteenthresist, is formed at a portion that becomes a shield section above thefirst semiconductor layer 30 a. The resist r7, which is a fourteenthresist, is formed on a portion that becomes a first gate electrode abovethe second semiconductor layer 30 b. The resist r8, which is a fifteenthresist, is formed on a portion that becomes a second gate electrodeabove the third semiconductor layer 30 c. Furthermore, the resist r9,which is a sixteenth resist, is formed on a portion that becomes a thirdgate electrode above the fourth semiconductor layer 30 d, and the resistr10, which is a seventeenth resist, is formed on a portion that becomesa fourth gate electrode above the fifth semiconductor layer 30 e.

Next, as shown in FIG. 6( c), the gate metal 34 is subjected to etchingsuch as dry etching or the like to form a shield section 34 a above thefirst semiconductor layer 30 a and to form first to fourth gateelectrodes 34 b to 34 e above the second to fifth semiconductor layers30 b to 30 e, respectively.

Next, as shown in FIG. 7( a), the shield section 34 a and the first tofourth gate electrodes 34 b to 34 e are subjected to etching such as dryetching or the like, for example. Furthermore, unnecessary gate metal 34at the shield section 34 a and at the first to fourth gate electrodes 34b to 34 e can be removed securely. Moreover, as a result, the shieldsection 34 a is formed to cover a portion of the first semiconductorlayer 30 a that becomes an intrinsic semiconductor region. The firstgate electrode 34 b is formed to cover a portion of the secondsemiconductor layer 30 b that becomes a channel region. The second gateelectrode 34 c is formed to cover portions of the third semiconductorlayer 30 c that become a channel region and an LDD region. The thirdgate electrode 34 d is formed to cover a portion of the fourthsemiconductor layer 30 d that becomes a channel region. The fourth gateelectrode 34 e is formed to cover a portion of the fifth semiconductorlayer 30 e that becomes a channel region.

Furthermore, by performing the aforementioned etching, the gateinsulating film 29 becomes a gate insulating film 29′ having astep-shaped pattern. The film thickness of exposed portions of the gateinsulating film 29′ is thinner than that of portions located below theshield section 34 a or the first to fourth gate electrodes 34 b to 34 e,the former being approximately ⅓ of the latter. As shown in FIG. 8( c),which is shown later, the gate insulating film 29′ is maintained in thestep-shaped pattern even after the shield section 34 a has been removed;however, it does not affect the photodiode at all. Furthermore, byperforming a prescribed etching treatment as described above, the shieldsection 34 a and the first to fourth gate electrodes 34 b to 34 e can beformed at appropriate locations with ease compared to a case in whichthe shield section 34 a and the first to fourth gate electrodes 34 b to34 e are formed by pinpointing by a sputtering method, for example.

Next, in FIG. 7( b), n-type low-concentration impurity ions (phosphorusions, for example) are implanted from above the shield section 34 a andthe first to fourth gate electrodes 34 b to 34 e. Thus, in the stepshown in FIG. 7( b), using the shield section 34 a and the first tofourth gate electrodes 34 b to 34 e as resists (masks), theaforementioned low-concentration phosphorus ions are doped inside thefirst to fifth semiconductor layers 30 a to 30 e.

Specifically, in the first semiconductor layer 30 a, low-concentrationphosphorus ions are implanted into regions that are not covered by theshield section 34 a to form impurity implanted regions 36 and 37. Aregion 35 of the first semiconductor layer 30 a where phosphorus ionswere not implanted becomes an intrinsic semiconductor region of thephotodiode. Furthermore, in the second semiconductor layer 30 b,low-concentration phosphorus ions are implanted into regions that arenot covered by the first gate electrode 34 b to form impurity implantedregions 39 and 40. A region 38 of the second semiconductor layer 30 bwhere phosphorus ions were not implanted becomes a channel region of theLDD configuration TFT.

In the third semiconductor layer 30 c, low-concentration phosphorus ionsare implanted to regions that are not covered by the second gateelectrode 34 c to form impurity implanted regions 42 and 43. The region38 of the third semiconductor layer 30 c where phosphorus ions were notimplanted becomes a channel region 41 and LDD regions 44 and 45 of aGOLD configuration TFT. In the fourth semiconductor layer 30 d,low-concentration phosphorus ions are implanted to regions that are notcovered by the third gate electrode 34 d to form impurity implantedregions 47 and 48. A region 46 of the fourth semiconductor layer 30 dwhere phosphorus ions were not implanted becomes a channel region of theSingle Drain configuration TFT. In the fifth semiconductor layer 30 e,low-concentration phosphorus ions are implanted into regions that arenot covered by the fourth gate electrode 34 e to form impurity implantedregions 50 and 51. A region 49 of the fifth semiconductor layer 30 ewhere phosphorus ions were not implanted becomes a channel region of theSingle Drain configuration TFT. The accelerating voltage duringphosphorus ion implantation is set at 80 kV, and the dose amount is setat 1×10¹³/cm², for example.

In a low-concentration phosphorus ion implantation step shown in FIG. 7(b), the shield section 34 a is used as a resist (mask). Therefore, theproductivity of the active matrix substrate 5 can be increasedsignificantly compared to a case in which the shield section 34 a is notprovided. Specifically, if the shield section 34 a is not formed, thefirst semiconductor layer 30 a for the photodiode needs to be covered bya resist when performing the step of FIG. 7( b). In contrast, in thepresent embodiment, a photomask step for providing the aforementionedresist can be omitted once. Therefore, the production costs, lead time,and the yield decrease can be reduced by approximately 7%, respectively,thereby improving the productivity of the active matrix substrate 5significantly.

Next, as shown in FIG. 7( c), resists r11, r12, r13, and r14, which aremasks, are formed above the first to fourth semiconductor layers 30 a to30 d. Specifically, the resist r11, which is a first resist, is formedso as to cover a left side portion of the first semiconductor layer 30a. The resist r11 functions as a mask along with the shield section 34a. The resist r12, which is a third resist, is formed so as to cover theoverall second semiconductor layer 30 b. The resist r13, which is aneighth resist, is formed so as to cover the overall third semiconductorlayer 30 c. The resist r14, which is a tenth resist, is formed so as tocover the overall fourth semiconductor layer 30 d.

Then, p-type high-concentration impurity ions (boron ions, for example)are implanted from above the resists r11 to r14 and the fourth gateelectrode 34 e. This way, a p-type region 52 is formed at the right sideportion of the first semiconductor layer 30 a, and a source region 53and a drain region 54 are formed in the fifth semiconductor layer 30 e.In addition, in the first semiconductor layer 30 a, the resist r11 andthe shield section 34 a prevent boron ions from being implanted into itsleft side portion and middle section. Furthermore, in the second tofourth semiconductor layers 30 b to 30 d, implantation of boron ions isprevented by the corresponding resists r12 to r14.

In the fifth semiconductor layer 30 e, phosphorus ions have beeninjected in the previous step. Because of this, in order to form thep-type source region 53 and the drain region 54 in this step,counter-doping needs to be performed in the fifth semiconductor layer 30e. Therefore, the dose amount needs to be set higher. Specifically, theaccelerating voltage during boron ion implantation is set at 80 kV, andthe dose amount is set at 3×10¹⁵/cm², for example.

Next, as shown in FIG. 8( a), resists r15, r16, and r17, which aremasks, are formed above the first, second, and fifth semiconductorlayers 30 a, 30 b, and 30 e. Specifically, the resist r15, which is asecond resist, is formed so as to cover a right side portion of thefirst semiconductor layer 30 a. The resist r15 functions as a mask alongwith the shield section 34 a. In addition, the resist r16, which is afourth resist, is formed so as to cover a portion of the secondsemiconductor layer 30 b that becomes a channel region and an LDDregion, and the resist r17, which is a twelfth resist, is formed so asto cover the overall fifth semiconductor layer 30 e.

Then, n-type high concentration impurity ions (phosphorus ions, forexample) are implanted from above the resists r15 to r17 and the secondand third gate electrodes 34 c and 34 d. This way, an n-type region 55is formed on the left side portion of the first semiconductor layer 30a. Furthermore, in the first semiconductor layer 30 a, the resist r15and the shield section 34 a prevent phosphorus ions from being implantedinto its right side edge and middle section, and an intrinsicsemiconductor region (i-layer) 56 is formed between the p-type region 52and the n-type region 55.

In the second semiconductor layer 30 b, a source region 57 and a drainregion 58 are formed in portions that are not covered by the resist r16,and LDD regions 59 and 60 are formed in portions covered by the resistr16 such that the channel region 38 is interposed between the LDDregions 59 and 60. In the third semiconductor layer 30 c, a sourceregion 61 and a drain region 62 are formed in portions that are notcovered by the second gate electrode 34 c. In the fourth semiconductorlayer 30 d, a source region 63 and a drain region 64 are formed inportions that are not covered by the third gate electrode 34 d. In thefifth semiconductor layer 30 e, the resist r17 prevents phosphorus ionsfrom being implanted. The accelerating voltage during phosphorus ionimplantation is set at 80 kV, and the dose amount is set at 3×10¹⁵/cm²,for example.

Other than the aforementioned description, the high-concentration boronion implantation step shown in FIG. 7( c) and the high-concentrationphosphorus ion implantation step shown in FIG. 8( a) may be performed ina reversed order.

Next, as shown in FIG. 8( b), a step for removing the shield section 34a is performed. Then, a resist r18 is formed so as to cover the overallsecond to fifth semiconductor layers 30 b to 30 e excluding the firstsemiconductor layer 30 a. Then, the first or second conductive type(n-type or p-type) impurity is implanted into the first semiconductorlayer 30 a to adjust the resistance of the aforementioned photodiode.Specifically, p-type low-concentration impurity ions (boron ions, forexample), for example, are implanted into the first semiconductor layer30 a from above the gate insulating film 29′ to adjust the resistance ofthe aforementioned photodiode. This way, the resistance of thephotodiode can be set at an appropriate value with ease. Theaccelerating voltage during boron ion implantation is set at 80 kV, andthe dose amount is set at 1×10¹³/cm², for example.

Next, as shown in FIG. 8( c), the resist r18 is removed to form aphotodiode 70, an LDD configuration n-channel type TFT 71 a, a GOLDconfiguration n-channel type TFT 71 b, a Single Drain configurationn-channel type TFT 71 c, and a p-channel type Single Drain configurationTFT 71 d.

Here, an “LDD region” in the present embodiment indicates a region inwhich the impurity concentration is 3×10¹⁷ atoms/cm³ or more and islower than the impurity concentration in a source region and a drainregion. Therefore, a region of a semiconductor layer that contains animpurity at a very low concentration (less than 3×10¹⁷ atoms/cm³) is notincluded in the LDD region. For example, there may be a case in which apart of an impurity implanted into an LDD region diffuses into a channelregion located below a gate electrode. However, such a portion is notincluded in the LDD region because the impurity concentration in theportion where the impurity diffused is considered very low.

As described above, in the method of manufacturing the active matrixsubstrate (semiconductor device) 5 of the present embodiment, the shieldsection 34 a is formed using the gate metal 34 so as to cover a portionof the photodiode 70 that becomes the intrinsic semiconductor region 56.As a result, variation in the channel length (dimension of the intrinsicsemiconductor region 56 in the horizontal direction of FIG. 8( c)) ofthe photodiode 70, i.e., variation in output characteristics of thephotodiode 70, can be suppressed. In forming a p-type region and ann-type region, if a resist is formed over a region that becomes anintrinsic semiconductor region in each of the steps of forming thep-type region and the n-type region, dimensional accuracy of theintrinsic semiconductor region is affected by dimensional accuracy andalignment of the respective resists. In contrast, as described above, inthe method of forming the shield section 34 a using the gate metal 34,the dimension of the intrinsic semiconductor region 56 is affected onlyby variation in the dimension of the shield section 34 a and errorsduring etching. Therefore, variation in the dimension can be suppressed.

Specifically, as shown in FIG. 9, according to the conventional method,dimensional variation of the intrinsic semiconductor region(2(a²+b²))^(1/2)) was determined by dimensional variations a and a andalignment variations b and b of the respective resists when forming thep-type region and the n-type region. In contrast, according to themethod of the present embodiment, a dimensional variation a of theresist when forming the shield section 34 a and a dimensional variationc at the time of etching mainly affect the dimensional variation((a²+c²)^(1/2)) of the intrinsic semiconductor region 56. Therefore, asshown in FIG. 9, the dimensional variation of the intrinsicsemiconductor region can be reduced compared to the conventional methodby using the method of the present embodiment. In the example of FIG. 9,the dimensional variation of the intrinsic semiconductor region was 1.08μm when the conventional method was used. The variation can be reducedto 0.58 μm by using the method of the present embodiment.

Here, in FIG. 9, dimensional variations in the respective steps arevalues obtained by taking into account 3σ relative to the average valueof dimensional errors. In addition, in FIG. 9, dimensional variations ofthe intrinsic semiconductor region according to the conventional exampleand the present embodiment are values calculated by equations in thetable.

In the present embodiment, the p-type region 52 and the n-type region 55(first and second conductive type regions) are formed in theaforementioned first semiconductor layer 30 a using the shield section34 a as a resist (mask), and then, the shield section 34 a is removed.Because of this, decrease in the light-receiving area of the intrinsicsemiconductor region 56 and resulting decrease in the amount of lightentering the intrinsic semiconductor region 56, which occur in theaforementioned conventional example, can be prevented. Therefore,lowering of photocurrent flowing into the photodiode 70 can beprevented. In addition, in the present embodiment, even when the shieldsection 34 a is formed using dry etching, etching damages in the shieldsection edges are on the p-type region 52 and the n-type region 55.Because of this, unlike the conventional example, lowering of the S/Nratio does not occur in output of the photodiode 70. As a result,according to the present embodiment, the high-performance photodiode 70in which variation in output characteristics and lowering of detectionaccuracy are suppressed can be formed.

The aforementioned embodiments are all shown as examples, and are notlimiting. Technical scope of the present invention is specified by thescope of claims, and all modifications within the scope that areequivalent to the configurations described therein are also included inthe technical scope of the present invention.

For example, in the aforementioned description, a case in which theaforementioned manufacture method is applied to the manufacture of anactive matrix substrate that is used in a liquid crystal display deviceequipped with a touch panel was described. However, the aforementionedmanufacture method is not limited to a method of manufacturing an activematrix substrate that is used in a liquid crystal display deviceequipped with a touch panel as long as it is a method of manufacturing asemiconductor device in which a photodiode and a thin film transistorare formed on a single substrate. Specifically, it can be applied to amethod of manufacturing various display devices, such assemi-transmissive and reflective liquid crystal panels, organic EL(Electronic Luminescence) element, inorganic EL element, field emissiondisplays, and the like, as well as active matrix substrates used inthem. Moreover, it can be applied to a method of manufacturing asemiconductor device in which a photodiode is used as an illuminancesensor (ambient sensor) to detect outside light.

Furthermore, in the aforementioned description, a case in which aphotodiode and four types of thin film transistors having mutuallydifferent configurations are formed on a single substrate was described.However, the types and the number of thin film transistors formed on thesame substrate as the photodiode are not limited to the aforementionedtypes and number. Thus, any configuration is possible as long as it usesa gate metal to form a shield section and a gate electrode over asemiconductor layer for a photodiode and over a semiconductor layer fora thin film transistor, respectively, and uses the shield section as aresist (mask). Specifically, a photodiode and any one type of theaforementioned four types of thin film transistors may be formed on asingle substrate, for example.

INDUSTRIAL APPLICABILITY

The present invention is useful with respect to a method ofmanufacturing a semiconductor device that can form a high-performancephotodiode in which variation in output characteristics and performancedeterioration are suppressed.

DESCRIPTION OF REFERENCE CHARACTERS

5 active matrix substrate (semiconductor device)

5′ base substrate

28 a to 28 e, 30 a to 30 e first to fifth semiconductor layers

29, 29′ gate insulating films

32, 33, 36, 37, 39, 40, 42, 43, 47, 48, 50, 51 impurity implantedregions

34 a shield section

34 b to 34 e first to fourth gate electrodes

38, 41, 46, 49 channel regions

44, 45, 59, 60 low-concentration impurity regions (LDD regions)

52 p-type region (second conductive type region)

55 n-type region (first conductive type region)

56 intrinsic semiconductor region

53, 57, 61, 63 source regions

54, 58, 62, 64 drain regions

70 photodiode

71 a to 71 d first to fourth thin film transistors

r1 to r18 resists

1. A method of manufacturing a semiconductor device having a photodiodeand a thin film transistor on a same substrate, the method comprising:(a) forming a first semiconductor layer for said photodiode and a secondsemiconductor layer for said thin film transistor on said substrate; (b)forming a gate insulating film that covers said first and secondsemiconductor layers; (c) forming a first gate electrode that covers aportion of said second semiconductor layer that becomes a channel regionon said gate insulating film using a prescribed gate metal, and forminga shield section that covers a portion of said first semiconductor layerthat becomes an intrinsic semiconductor region on said gate insulatingfilm using said gate metal; (d) implanting a first conductive typeimpurity into said first and second semiconductor layers from above saidgate insulating film to form a region where said first conductive typeimpurity is implanted in a region of said first semiconductor layer thatis not covered by said shield section and to form a region where saidfirst conductive type impurity is implanted in a region of said secondsemiconductor layer that is not covered by said first gate electrode;(e) forming a first resist having an opening that exposes a portion ofsaid gate insulating film, which covers said first semiconductor layer,and implanting a second conductive type impurity from above said gateinsulating film to form a second conductive type region in a region ofsaid first semiconductor layer that is not covered by said shieldsection or said first resist; (f) forming a second resist that coverssaid second conductive type region of said first semiconductor layer andimplanting said first conductive type impurity from above said gateinsulating film to form a first conductive type region in a region ofsaid first semiconductor layer that is not covered by said shieldsection or said second resist; and (g) removing said shield section. 2.The method of manufacturing a semiconductor device according to claim 1,wherein in said step (e), a third resist that entirely covers saidsecond semiconductor layer is formed to prevent said second conductivetype impurity from being implanted into said second semiconductor layer,and wherein in said step (f), a fourth resist having an opening thatexposes portions of said gate insulating film that are located on bothsides of said second semiconductor layer with said gate electrodelocated therebetween in a plan view is formed so that one and the otherof a source region and a drain region are respectively formed in regionsof said both sides of said second semiconductor layer that are notcovered by said first gate electrode or said fourth resist, and a regionof said second semiconductor layer that is covered by said fourth resistbecomes a low-concentration impurity region to form a first conductivetype thin film transistor having an LDD configuration as a first of saidthin film transistor.
 3. The method of manufacturing a semiconductordevice according to claim 2, wherein in said step (a), a thirdsemiconductor layer for a second thin film transistor is formed on saidsubstrate, wherein in said step (b), a gate insulating film that coverssaid first to third semiconductor layers is formed, wherein beforeperforming said step (c), the method further includes a step (h) offorming fifth and sixth resists that respectively cover said first andsecond semiconductor layers entirely and forming a seventh resist thatcovers a portion of said third semiconductor layer that becomes achannel region, and implanting a first conductive type impurity intosaid third semiconductor layer from above said gate insulating film toform a region in which said first conductive type impurity is implantedin a region of said third semiconductor layer that is not covered bysaid seventh resist, wherein in said step (c), a second gate electrodethat covers portions of said third semiconductor layer that become achannel region and a low-concentration impurity region is formed on saidgate insulating film using said gate metal, wherein in said step (d),said channel region and said low-concentration impurity region areformed in a region that is covered by said second gate electrode,wherein said step (e), an eighth resist that entirely covers said thirdsemiconductor layer is formed to prevent said second conductive typeimpurity from being implanted to said third semiconductor layer, andwherein in said step (f), one and the other of a source region and adrain region are respectively formed in regions of said thirdsemiconductor layer that are not covered by said second gate electrodeto form a first conductive type thin film transistor having a GOLDconfiguration as said second thin film transistor.
 4. The method ofmanufacturing a semiconductor device according claim 3, wherein in saidstep (a), a fourth semiconductor layer for a third thin film transistoris formed on said substrate, wherein in said step (b), a gate insulatingfilm that covers said first to fourth semiconductor layers is formed,wherein in said step (h), a ninth resist that entirely covers saidfourth semiconductor layer is formed, wherein in said step (c), a thirdgate electrode that covers a portion of said fourth semiconductor layerthat becomes a channel region is formed on said gate insulating filmusing said gate metal, wherein in said step (d), a region in which saidfirst conductive type impurity is implanted is formed in a region ofsaid fourth semiconductor layer that is not covered by said third gateelectrode, wherein in said step (e), a tenth resist that entirely coverssaid fourth semiconductor layer is formed to prevent said secondconductive type impurity from being implanted to said fourthsemiconductor layer, and wherein in said step (f), one and the other ofa source region and a drain region are respectively formed in regions ofsaid fourth semiconductor layer that are not covered by said third gateelectrode to form a first conductive type thin film transistor having aSingle Drain configuration as said third thin film transistor.
 5. Themethod of manufacturing a semiconductor device according to claim 4,wherein in said step (a), a fifth semiconductor layer for a fourth thinfilm transistor is formed on said substrate, wherein in said step (b), agate insulating film that entirely covers said first to fifthsemiconductor layers is formed, wherein in said step (h), an eleventhresist that entirely covers said fifth semiconductor layer is formed,wherein in said step (c), a fourth gate electrode that covers a portionof said fifth semiconductor layer that becomes a channel region isformed on said gate insulating film using said gate metal, wherein insaid step (d), a region in which said first conductive type impurity isimplanted is formed in a region of said fifth semiconductor layer thatis not covered by said fourth gate electrode, wherein in said step (e),one and the other of a source region and a drain region are respectivelyformed in regions of said fifth semiconductor layer that are not coveredby said fourth gate electrode to form a second conductive type thin filmtransistor as said fourth thin film transistor, and wherein in said step(f), a twelfth resist that entirely covers said fifth semiconductorlayer is formed to prevent said first conductive type impurity frombeing implanted to said fifth semiconductor layer.
 6. The method ofmanufacturing a semiconductor device according to claim 5, wherein insaid step (c), after said gate metal is formed on said gate insulatingfilm so as to entirely cover said first to fifth semiconductor layers,thirteenth, fourteenth, fifteenth, sixteenth, and seventeenth resistsare formed at portions that become said shield section, said first, saidsecond, said third, and said fourth gate electrodes, respectively, and aprescribed etching treatment is performed to form said shield sectionand said first to fourth gate electrodes on said gate insulating film.7. The method of manufacturing a semiconductor device according to claim5, wherein after said step (b), the method further includes a step (i)of implanting said first or said second conductive type impurity intosaid first to fifth semiconductor layers from above said gate insulatingfilm to adjust a resistance of said respective first to fourth thin filmtransistors.
 8. The method of manufacturing a semiconductor deviceaccording to claim 1, wherein after said step (g), the method furtherincludes a step (j) of implanting said first or said second conductivetype impurity into said first semiconductor layer from above said gateinsulating film to adjust a resistance of said photodiode.
 9. The methodof manufacturing a semiconductor device according to claim 1, whereinsaid first conductive type is an n-type and said second conductive typeis a p-type.